In recent years, a technology called a smart grid has gained attention. The smart grid is a technical framework to realize efficient power usage by constructing a new transmission network having a communication channel along with the transmission network and using the intelligent transmission network. The idea of the smart grid, as a background, is to realize efficient management of power usage, swift handling of an incident when such an incident occurs, remote control of power usage, distributed power generation using power generation facilities outside the control of a power company, or charging management of an electric vehicle. Particularly, effective utilization of in-house power generating stations using renewable energy by ordinary households or operators other than power companies and charging management of various motor-driven movable bodies typically including electric vehicles have attracted considerable attention. Incidentally, renewable energy is energy generated without using fossil fuel.
Power generated by ordinary households or operators other than power companies is used by power generation operators. Excessive power after being used by the power generation operators is currently purchased by power companies. However, purchasing power supplied from power generation facilities outside the control of a power company is a heavy burden to the power company. For example, amount of power supplied from photovoltaic power generation facilities depends on the weather. Moreover, amount of power supplied from in-house power generating stations of ordinary households depends on power usage of ordinary households that largely changes day by day. Thus, it is difficult for power companies to receive stable power supply from power generation facilities outside the control of power companies. For the above reason, it may be difficult for power companies to purchase power in the future.
Thus, a home battery initiative that uses power generated by power generation facilities outside the control of power companies after being temporarily stored in batteries has recently gained attention. For example, a method of using power generated by photovoltaic power generation facilities by storing such power in batteries and making up for shortages in the night or when the weather is bad is considered. Further, methods of limiting amount of power received from a power company in accordance with the battery storage amount and using power stored in batteries in the daytime when power rates are higher by storing power in batteries supplied by a power company in the night when power rates are lower are considered. Batteries can store power as DC, which eliminates the need for DC/AC conversion or AC/DC conversion during transmission so that losses during conversion can be reduced.
Thus, various expectations regarding power management mingle with one another amid the smart grid initiative. To realize such power management, the smart grid initiative is premised on having a communication channel along with a transmission network. That is, exchanging information about power management by using the intelligent transmission network is assumed. However, in a region where a communication infrastructure has been built, instead of using a transmission network as a communication channel, information about power management may be exchanged by using a network constructed by the deployed communication infrastructure. That is, what is important in the smart grid initiative is how efficiently to use power generation facilities and storage facilities that are not managed in a unified manner.
Regarding the above power management, for example, Patent Literature 1 describes a power management system for stably supplying power by temporarily storing, in a battery, power obtained by using a renewable energy power generation system. In other words, Patent Literature 1 discloses an idea similar to the home battery initiative. Certainly, stable supply of renewable energy is one of major issues. Some of the issues associated with stable supply of renewable energy may be solved by appropriately managing charging/discharging of a battery.